A recent clinical trial has uncovered an intriguing link between a commonly used diabetes medication and the risk of long COVID. According to Dr. Carolyn Bramante, the lead author of the study from the University of Minnesota, "our study showed that metformin, a safe, affordable, and widely accessible medication, significantly reduces the likelihood of developing long COVID if taken immediately after contracting the coronavirus."
The clinical trial, published in the Lancet, examined the effects of metformin, a medication prescribed for patients with type 2 diabetes and diabetes mellitus, as well as fluvoxamine, a treatment of obsessive-compulsive disorder, and the infamous de-worming medication ivermectin. The researchers found individuals who tested positive for COVID-19 and were taking metformin were 40% less likely (relative reduction rate) to develop long COVID. It's important to note that the trial results do not address whether metformin could effectively treat individuals already experiencing long COVID. "There is an urgent need to find potential treatments and preventive measures for this disease," explains Bramante.
However, it's crucial to avoid taking the 40% reduction statistic out of context. Researchers who investigate how different ways of presenting statistics affect overall impressions warn that the traditional measure of success, relative risk, can lead to an "overestimation of therapeutic effectiveness."
In the Lancet study, which focused on obese and overweight individuals, those who took metformin within three days of testing positive for COVID-19 experienced a 4.1% decrease in the incidence of long COVID after ten months. This percentage is called the absolute reduction rate. It measures the difference in the percentage of cases reporting long COVID in the metformin group (6.3%) versus the metformin-control group (10.4%).
It's important to note that relative reductions are usually larger, often misunderstood by clinicians and the public, and tend to generate sensationalist coverage. Bramante et al. presented both statistics in their study.
While the absolute difference may seem small, the study still suggests that there are mechanisms that can be triggered with medications during a COVID-19 infection that decrease the risk of long COVID. Nonetheless, questions about the prevalence and underlying causes of long COVID during this pandemic remain. According to Akiko Iwasaki, Ph.D., an expert unaffiliated with the study, possible causes of long COVID include "persistent virus infection, as well as autoimmunity, and reactivation of latent like the Epstein-Barr virus as well as chronic changes that happen in tissues due to inflammation." She also speculates that long COVID encompasses various disorders with overlapping symptoms, making it challenging to determine the responsible mechanisms.
Future clinical reach will likely include non-overweight participants and may provide insights into currently unknown biological pathways to target. Metformin, which is affordable and widely accessible, is also known for its minimal potential for drug interactions. Some common name brands of metformin include Fortamet, Glucophage, Glumetza, and Riomet.
Sources: The Lancet, Mayo Clinic, AAFP, Cardiologia, EurekAlert!